Selecting broilers for low or high abdominal fat: Distribution of carcass fat and quality of meat

The increasing use of unconventional feedstuffs in chicken's diets results in the substitution of starch by lipids as the main dietary energy source. To evaluate the responses of genetically fat or lean chickens to these diets, males of two experimental lines divergently selected for abdominal fat content were fed isocaloric, isonitrogenous diets with either high lipid (80 g/kg), high fiber (64 g/kg) contents (HL), or low lipid (20 g/kg), low fiber (21 g/kg) contents (LL) from 22 to 63 days of age. The diet had no effect on growth performance and did not affect body composition evaluated at 63 days of age. Glycolytic and oxidative energy metabolisms in the liver and glycogen storage in liver and Sartorius muscle at 63 days of age were greater in chicken fed LL diet compared with chicken fed HL diet. In Pectoralis major (PM) muscle, energy metabolisms and glycogen content were not different between diets. There were no dietary-associated differences in lipid contents of the liver, muscles and abdominal fat. However, the percentages of saturated (SFA) and monounsaturated fatty acids (MUFA) in tissue lipids were generally higher, whereas percentages of polyunsaturated fatty acids (PUFA) were lower for diet LL than for diet HL. The fat line had a greater feed intake and average daily gain, but gain to feed ratio was lower in that line compared with the lean line. Fat chickens were heavier than lean chickens at 63 days of age. Their carcass fatness was higher and their muscle yield was lower than those of lean chickens. The oxidative enzyme activities in the liver were lower in the fat line than in the lean line, but line did not affect energy metabolism in muscles. The hepatic glycogen content was not different between lines, whereas glycogen content and glycolytic potential were higher in the PM muscle of fat chickens compared with lean chickens. Lipid contents in the liver, muscles and abdominal fat did not differ between lines, but fat chickens stored less MUFA and more PUFA in abdominal fat and muscles than lean chickens. Except for the fatty acid composition of liver and abdominal fat, no interaction between line and diet was observed. In conclusion, the amount of lipids stored in muscles and fatty tissues by lean or fat chickens did not depend on the dietary energy source.Keywords: chicken, energy metabolism, fatty acid composition, lipid deposition, starch ImplicationsBroiler production is facing to an increasing incorporation (Slominski et al., 2004; Bregendhal, 2008) of unconventional feedstuffs (rapeseed meal, beet pulps, palm kernel cake and distiller's dried grains with solubles) containing more fibers in diets. To restore suitable energy content, fat may be added to fiber rich diets, so that energy source is changed from starch to lipids. Divergently selected chicken lines for body fatness are pertinent experimental models to unravel energy metabolism pathways and body composition and to test possible interactions between genetics and nutrition. Our study showed that these lines are able to use starch ...

Section: Discussionsupporting

confidence: 82%

The ability of genetically lean or fat slow-growing chickens to synthesize and store lipids is not altered by the dietary energy source

Baéza

Gondret

Chartrin

et al. 2015

“…However, the genetic dissociation between carcass fat content and IMF content by selection is possible. Examples are given in chickens in which two lines divergently selected for abdominal fat level (1.4% v. 3.93%, Berri et al, 2005) did not display any differences in IMF level in thigh and breast muscles (Ricard et al, 1983;Berri et al, 2005). Another example is the divergent selection for IMF content in trout that lead to a lean muscle line with IMF lower than 5% and a fatty muscle line with IMF up to 10% without any significant difference in whole body fat content (Kolditz et al, 2008).…”

Section: Genetic and Genomic Markers Of Imf Contentmentioning

confidence: 99%

Intramuscular fat content in meat-producing animals: development, genetic and nutritional control, and identification of putative markers

Hocquette

Gondret

Baéza³

et al. 2010

655

447

Intramuscular fat (IMF) content plays a key role in various quality traits of meat. IMF content varies between species, between breeds and between muscle types in the same breed. Other factors are involved in the variation of IMF content in animals, including gender, age and feeding. Variability in IMF content is mainly linked to the number and size of intramuscular adipocytes. The accretion rate of IMF depends on the muscle growth rate. For instance, animals having a high muscularity with a high glycolytic activity display a reduced development of IMF. This suggests that muscle cells and adipocytes interplay during growth. In addition, early events that influence adipogenesis inside the muscle (i.e proliferation and differentiation of adipose cells, the connective structure embedding adipocytes) might be involved in interindividual differences in IMF content. Increasing muscularity will also dilute the final fat content of muscle. At the metabolic level, IMF content results from the balance between uptake, synthesis and degradation of triacylglycerols, which involve many metabolic pathways in both adipocytes and myofibres. Various experiments revealed an association between IMF level and the muscle content in adipocyte-type fatty acid-binding protein, the activities of oxidative enzymes, or the delta-6-desaturase level; however, other studies failed to confirm such relationships. This might be due to the importance of fatty acid fluxes that is likely to be responsible for variability in IMF content during the postnatal period rather than the control of one single pathway. This is evident in the muscle of most fish species in which triacylglycerol synthesis is almost zero. Genetic approaches for increasing IMF have been focused on live animal ultrasound to derive estimated breeding values. More recently, efforts have concentrated on discovering DNA markers that change the distribution of fat in the body (i.e. towards IMF at the expense of the carcass fatness). Thanks to the exhaustive nature of genomics (transcriptomics and proteomics), our knowledge on fat accumulation in muscles is now being underpinned. Metabolic specificities of intramuscular adipocytes have also been demonstrated, as compared to other depots. Nutritional manipulation of IMF independently from body fat depots has proved to be more difficult to achieve than genetic strategies to have lipid deposition dependent of adipose tissue location. In addition, the biological mechanisms that explain the variability of IMF content differ between genetic and nutritional factors. The nutritional regulation of IMF also differs between ruminants, monogastrics and fish due to their digestive and nutritional particularities.

“…This effect of dietary protein level on muscle glycogen level could be mediated by AMPK phosphorylation levels. Selection for low or high AF did not affect the lipid content of thigh and breast muscles (Ricard et al, 1983;Berri et al, 2005). Regarding the composition of intramuscular lipids of thigh muscles (triglycerides, phospholipids, free cholesterol and free fatty acids), Ricard and Leclercq (1984) found no significant difference between FL and LL chickens.…”

Section: Growth and Body Compositionmentioning

confidence: 99%

Chicken lines divergent for low or high abdominal fat deposition: a relevant model to study the regulation of energy metabolism

Baéza¹,

Bihan-Duval²

2013

Divergent selection of chickens for low or high abdominal fat (AF) but similar BW at 63 days of age was undertaken in 1977. The selection programme was conducted over seven successive generations. The difference between lines was then maintained constant at about twice the AF in the fat line as in the lean line. The aims of the first studies on these divergent chicken lines were to describe the growth, body composition and reproductive performance in young and adult birds. The lines were then used to improve the understanding of the relationship between fatness and energy and protein metabolism in the liver, muscle and adipose tissues, as well as the regulation of such metabolism at hormonal, gene and hypothalamic levels. The effects on muscle energy metabolism in relation to meat quality parameters were also described. This paper reviews the main results obtained with these lines.